Heat sink applicable for eletromagnetic device

ABSTRACT

The present disclosure provides a heat sink applicable for electromagnetic device comprises a first panel, a second panel, and a plurality of supporting structures connecting with the first panel and the second panel. Wherein the first panel, the second panel and the supporting structures together constitute a plurality of medium channels for cooling medium flowing therethrough. Wherein at least some of the medium channels are provided with openings formed on the first and/or second panels, and no close conductive loop is formed on cross section perpendicular to a medium flowing direction of the medium channels with the openings. Wherein a total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefits of Chinese Patent Application No. 201210413065.X, filed on Oct. 25, 2012 in the State Intellectual Property Office of China, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a heat sink applicable for the electromagnetic device.

BACKGROUND

As the energy efficient products and green energy are widely recognized and greatly developed, wind power converter, solar converter, middle-high voltage drive and power quality management device are widely applied. The heat dissipation problem generated from the high-power electromagnetic device such as reactor and transformer becomes more obvious. Thereby it becomes more important to develop a heat sink applicable for the electromagnetic device.

The working electromagnetic device will consume some power, which is converted into heat. The cooling to the electromagnetic component is required for the normal operation thereof In the air-cooling electromagnetic device such as reactor or transformer, the insulated supports are provided between the iron core and coil, between the coil layers or inside the coil to define the air channel. The cold air enters from one end of the air channel and moves along the axial direction of the coil, and is transformed into the hot air through the heat exchange with the wall surface of the air channel. After that, the hot air is blown out from the other end of the air channel for cooling the electromagnetic component. The air-cooling mode has disadvantages that the heat transfer coefficient is low, the heat transfer area is difficult to enlarge due to dependence on the air channel surface area, and the cooling efficiency thus is low. In many cases, the conventional cooling method is unable to meet the cooling demand of the high-power electromagnetic device.

SUMMARY

The present disclosure is to provide a heat sink applicable for electromagnetic device of low eddy current loss and high cooling efficiency, to overcome the disadvantage of low cooling efficiency in the related art.

On one aspect, the present disclosure provides a heat sink applicable for electromagnetic device comprises a first panel, a second panel, and a plurality of supporting structures connecting with the first panel and the second panel. Wherein the first panel, the second panel and the supporting structures together constitute a plurality of medium channels for cooling medium flowing therethrough. Wherein at least some of the medium channels are provided with openings formed on the first and/or second panels, and no close conductive loop is formed on cross section perpendicular to a cooling medium flowing direction of the medium channels with the openings. Wherein a total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel.

On another aspect, the present disclosure provides a heat sink applicable for electromagnetic device comprises a first panel, a second panel, a middle substrate between the first panel and the second panel, and a plurality of supporting structures connecting with the first panel and the middle substrate and connecting with the second panel and the middle substrate respectively. Wherein the first panel and the middle substrate and the supporting structures together with the second panel and the middle substrate and the supporting structures constitute two layers of multiple medium channels for cooling medium flowing therethrough. Wherein at least some of the medium channels are provided with openings formed on the first and/or second panels, and no close conductive loop is formed on a cross section perpendicular to cooling medium flowing direction of the medium channels with the openings. A total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein:

FIG. 1A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the first embodiment in the present disclosure.

FIG. 1B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the first embodiment in the present disclosure shown in FIG. 1A.

FIG. 2A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the second embodiment in the present disclosure.

FIG. 2B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the second embodiment in the present disclosure shown in FIG. 2A.

FIG. 3A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the third embodiment in the present disclosure.

FIG. 3B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the third embodiment in the present disclosure shown in FIG. 3A.

FIG. 4A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the forth embodiment in the present disclosure.

FIG. 4B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the forth embodiment in the present disclosure shown in FIG. 4A.

FIG. 5A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the fifth embodiment in the present disclosure.

FIG. 5B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the fifth embodiment in the present disclosure shown in FIG. 5A.

FIG. 6A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the sixth embodiment in the present disclosure.

FIG. 6B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the sixth embodiment in the present disclosure shown in FIG. 6A.

FIG. 7A is a perspective schematic view of the heat sink applicable for the electromagnetic device of the seventh embodiment in the present disclosure.

FIG. 7B is a cross-sectional view of the heat sink applicable for the electromagnetic device of the seventh embodiment in the present disclosure shown in FIG. 7A.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention are described more fully hereinafter with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity.

The concept of the present disclosure is that, openings are defined on the medium channels of the heat sink, which can reduce the additional eddy current loss when the heat sink dissipates the heat from the electromagnetic device. In this case, the cooling efficiency is improved; a total area of all opening is less than 50% of an area of the plate thereof, for preventing too large opening from reducing the heat-exchange area with the electromagnetic device. Therefore, enough effective heat transfer area between the heat sink and the electromagnetic device is ensured, the eddy current loss is reduced, and thereby the heat sink can reach a maximum cooling effect.

The above and other technical content, feature and effect will be illustrated in detail referring to the accompany drawings and the following embodiments.

First Embodiment

FIGS. 1A and 1B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the first embodiment of the present invention. The heat sink of the first embodiment is a double-side-open type of multi-channel flat heat sink comprising a first panel 201, a second panel 202 and a plurality of supporting structures 203 (e.g., separator) in connection with the first panel 201 and the second panel 202. The first panel 201, the second panel 202 and the plurality of supporting structures 203 together constitute a plurality of medium channels 204. The first panel 201, the second panel 202 and the supporting structures 203 are made of, for example, a good thermal conductive material such as a metallic material. For example, the first panel 201, the second panel 202 and the supporting structure 203 are made of copper, aluminum, or aluminum alloy.

In the first embodiment, the first panel 201 and the second panel 202 are parallel to each other and are flat-shaped. The supporting structure 203 is also plate-shaped, and thereby the medium channel 204 is rectangular. The first panel 201 and the second panel 202 are unnecessary to be parallel to each other, and may form an angle with each other. The first panel 201 and the second panel 202 are not limited to flat shape, but may have other shapes such as arc-plate shape. Accordingly, the cross section of the medium channel may be in a variety of shapes, such as triangular shape, circular shape, oval shape, trapezoid shape and irregular shape. The medium channel may have any cross-sectional shape, as long as the airflow (e.g., air) may enter into one end and flow from the other end of the medium channel. In order to reduce the eddy current loss of the heat sink caused by the induced electric field due to the alternating magnetic field when the heat sink is used for the electromagnetic equipment, an opening 205 is defined on each medium channel 204 along longitudinal direction (cooling medium flowing direction), and a plurality of openings 205 are defined on a plurality of medium channels respectively. In the first embodiment, a plurality of openings 205 are uniformly arranged on the first panel 201 and the second panel 202 respectively. The openings 205 on the first panel 201 alternate with those on the second panel 202, i.e., openings 205 of adjacent medium channels 204 are defined on the first panel 201 and the second panel 202 respectively. In detail, the opening 205 of the first medium channel 204 is defined on the first panel 201, the opening 205 of the second medium channel 204 is defined on the second panel 202, and the opening 205 of the third medium channel 204 is defined on the first panel 201, and so on. The setting of the opening 205 is such that each cross section of the medium channel perpendicular to the cooling medium flowing direction does not have the close conductive loop formed, thereby making the current circuit open. For example, as shown in FIGS. 1A and 1B, the forth medium channel 204A is surrounded by the forth supporting structure 203A, the fifth supporting structure 203B, the first panel 201, and the second panel 202. The forth opening 205A is defined on the second panel 202 and extends along the longitudinal direction and over the full length (substantially consistent with the cooling medium flowing direction) of the forth medium channel 204A. Therefore, each lateral cross section perpendicular to the longitudinal direction of the forth medium channel 204A is provided with the forth opening 205A. In this case, the end-to-end connection of the forth supporting structure 203A, the first panel 201, the fifth supporting structure 203B, and the second panel 202 on the lateral cross section is broken by the forth opening 205A without forming a conductive loop.

When the heat sink of the first embodiment is employed to dissipate heat from the electromagnetic equipment, the first panel 201 and the second panel 202 of the heat sink are in close contact with the coil layer and the iron core of the electromagnetic equipment respectively to constitute the thermal interface, or the first panel 201 and the second panel 202 of the heat sink are in close contact with the adjacent coil layers of the electromagnetic equipment respectively to constitute the thermal interface. At the same time, the opening 205 of the medium channels 204 is blocked by the coil layer in close contact with the first panel 201 or the iron core in close contact with the second panel 202, thereby constituting the independent medium channel 204 with closed sidewall and the inner surface thereof is used for a heat-exchange surface. It should be noted that the first panel 201 and the second panel 202 of the heat sink are in close contact with the coil layer and the iron core of the electromagnetic equipment respectively through an insulating layer, or the first panel 201 and the second panel 202 of the heat sink are in close contact with the adjacent coil layers of the electromagnetic equipment respectively through the insulating layer. A large quantity of heat generated from the coil and the iron core during the operation of the electromagnetic equipment is transmitted from the coil layer and/or the iron core to the first panel 201 and/or the second panel 202 and the supporting structures 203 of the heat sink, i.e., to the surface of the medium channel 204. The cold medium enters into one end of a plurality of independent medium channels 204, flows through the medium channel 204 and exchanges heat with the surface of the medium channel 204, and then leaves the other end of the medium channel 204 and takes away a quantity of heat for the purpose of cooling the electromagnetic device.

In order to achieve larger thermal interface between the first panel 201 or the second panel 202 of the heat sink in the first embodiment and the coil layer or the iron core, a total area of all openings 205 on the first panel 201 is less than 50% of an area of the first panel 201, and a total area of all openings 205 on the second panel 202 is less than 50% of an area of the second panel 202. In order to further reduce the area of the openings, total area of all openings 205 on the first panel 201 is equal to or less than 40% of an area of the first panel 201, and a total area of all openings 205 on the second panel 202 is equal to or less than 40% of an area of the second panel 202.

The purpose of defining the opening 205 on the medium channel 204 is to make it impossible to form the closed loop at the medium channels 204 of the heat sink under the induction voltage of the alternating magnetic field, thereby significantly reducing the eddy current loss caused by electromagnetic induction. The heat sink of the first embodiment is employed to a single-phase iron core reactor, total area of the openings 205 on the first panel 201 of the heat sink is equal to 40% of an area of the first panel 201, and total area of the openings 205 on the second panel 202 of the heat sink is equal to 40% of an area of the second panel 202. In this case, the finite element simulation on 350 Hz seventh harmonic wave leads to a conclusion that the eddy current loss of the double-side-open type of multi-channel heat sink of the present first heat sink is less than 10% of an total loss of the single-phase iron core reactor, and is much less than that of the single-phase iron core reactor without the opening.

In the first heat sink mentioned above, one opening is defined on each medium channel. It is also feasible that only some of medium channels are provided with the openings and the others are not provided with the opening. Compared with the conventional heat sink of which all medium channels without the openings, on the base of ensuring the good cooling effect in the application of the electromagnetic device, the eddy current loss is greatly reduced.

Second Embodiment

FIGS. 2A and 2B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device of the second embodiment in the present invention. The heat sink of the second embodiment is a single-side-open type of multi-channel flat heat sink. It differs from the first embodiment in that the openings 205 of the medium channels 204 are entirely defined on the second panel 202, thereby no openings are defined on the first panel 201. Without a doubt, it is feasible that all openings 205 may be entirely defined on the first panel 201, thereby no openings are defined on the second panel 202.

Other part of the structure of the second heat sink is the same as that of the first heat sink, and the detailed description thereof is omitted herein.

Third Embodiment

FIGS. 3A and 3B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the third embodiment of the present invention. The third heat sink is a double-side-open type of multi-layer multi-channel flat heat sink comprising a first panel 201, a second panel 202, a middle substrate 206, a plurality of supporting structures 203 in connection with the first panel 201 and the middle substrate 206, and a plurality of supporting structures 203 in connection with the second panel 202 and the middle substrate 206. The first panel 201, the middle substrate 206 and a plurality of supporting structures 203 together constitute a plurality of medium channels 204 referring to as the first-layer medium channel. The openings 205 of each medium channel 204 in the first-layer medium channel are defined on the first panel 201, and total area of all openings 205 on the first panel 201 is less than 50% of an area of the first panel 201. The second panel 202, the middle substrate 206 and a plurality of supporting structures 203 together constitute a plurality of medium channels 204 referring to as the second-layer medium channel. The openings 205 of each medium channel 204 in the second-layer medium channel are defined on the second panel 202, and total area of all openings 205 on the second panel 202 is less than 50% of an area of the second panel 202. The first-layer medium channels and the second-layer medium channels share one middle substrate 206, thereby forming a double-side-open type of multi-layer and multi-channel flat heat sink with two layers of medium channels. In the third embodiment, the openings 205 at each medium channel 204 in the first-layer medium channel are arranged corresponding to the openings 205 at each medium channel 204 in the second-layer medium channel. However, the invention is not limit thereto. The openings 205 at each medium channel 204 in the two layers of medium channel are offset with respect to each other. The first panel 201, the second panel 202 and the middle substrate 206 may or may not be parallel to one another. Respective shapes thereof may be flat or arc-plate, and so on. The first panel 201, the second panel 202 and the middle substrate 206 are, for example, made of material having good thermal conductivity like metal. For example, they may be made of copper, aluminum or aluminum alloy.

In the double-side-open type of multi-layer multi-channel flat heat sink of the third embodiment, the first-layer medium channel and the second-layer medium channel are similar to the single-side-open type of multi-channel flat heat sink as shown in FIGS. 2A and 2B, and thereby the double-side-open type of multi-layer and multi-channel flat heat sink of the third embodiment can be approximately regarded as two single-side-open type of multi-channel flat heat sinks being back-to-back laminated together and share one middle substrate. Other part of the double-side-open type of multi-layer and multi-channel flat heat sink of the third embodiment such as the cross-sectional shape of the medium channel 204 is the same as that of the second embodiment, and the detailed description thereof is omitted herein. At the same time, when the double-side-open type of multi-layer and multi-channel flat heat sink of the third embodiment is applied to the electromagnetic device, the installation thereof is the same as that of the double-side-open type of multi-channel flat heat sink of the first embodiment, and the detailed description thereof is omitted herein. In the third embodiment, the heat sink has larger heat transfer area and better cooling effect, due to having two layers of medium channels.

Forth Embodiment

FIGS. 4A and 4B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the forth embodiment of the present invention. The heat sink of the forth embodiment is a punch-formed multi-channel flat heat sink comprising a first panel 201, a second panel 202 and a plurality of supporting structures 203 in connection with the first panel 201 and the second panel 203. The supporting structures 203, the first panel 201 and the second panel 202 together constitute a plurality of medium channels 204. One opening 205 is defined at each medium channel. The openings 205 of two adjacent medium channels 204 are defined on the first panel 201 and the second panel 202 respectively, and the openings 205 on the first panel 201 alternate with that on the second panel 202. The total area of all openings 205 on the first panel 201 is less than 50% of an area of the first panel 201, and the total area of the openings 205 on the second panel 202 is less than 50% of an area of the second panel 202.

For example, the heat sink of the forth embodiment is made of plate of copper, aluminum or aluminum alloy by means of mold punch forming process or by repeating bending process. In the forth embodiment, the medium channel 204 is, for example, trapezoid, U-shaped, V-shaped, circular or oval-shaped. However, the invention is not limited thereto. The plate of copper, aluminum or aluminum alloy is transformed into a trapezoid medium channel type of multi-channel by means of mold punch forming process, the thickness of the first panel 201, the second panel 202 and the supporting structure 203 is substantially the same as each other and can be formed into relatively thin, thereby the weight is decreased and the cost is saved. Of course, the material of the heat sink of the forth embodiment is not limited to copper, aluminum or aluminum alloy. Other materials of good thermal conductivity, which can be easily bent and transformed, are also feasible.

Other part of the heat sink of the forth embodiment is the same as that of the first embodiment and the detailed description thereof is omitted herein. At the same time, the installation of the heat sink of the forth embodiment applied to the electromagnetic device is the same as that of the double-side-open type of multi-channel flat heat sink of the first embodiment applied to the electromagnetic device, and the detailed description thereof is omitted herein.

Fifth Embodiment

FIGS. 5A and 5B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the fifth embodiment of the present invention. The heat sink of the fifth embodiment is a multi-channel flat heat sink with an insulating seal. The difference between the fifth embodiment and the second embodiment is that the opening 205 of each medium channel 204 is filled with or installed with an insulating seal 207. The insulating seal 207 may be made of a homogenous material such as resin different from the material of the heat sink itself, or composite material of a variety of materials such as metals and insulating materials as long as the insulating material exists between the metal, which may be the same as or different from the material of the heat sink to avoid electrical connection. In practice, the openings 205 of a part of the medium channels 204 may be provided with the insulating seals 207, but the opening 205 of other part of the medium channels 204 may not be provided with the insulating seal 207.

In the fifth heat sink, since the insulating seal 207 as a whole is not conductive, the conductive loop cannot be formed at any cross section perpendicular to the medium flowing direction of the medium channel 204 having the insulating seal 207. Thus, the eddy current loss is reduced when the heat sink is applied to the electromagnetic device. Meanwhile, the medium channel 204 having the insulating seal 207 may define a sidewall-closed channel by itself, and there is no need to block the opening 205 of the medium channel 204 with the use of the coil or the iron core of the installed electromagnetic device. Therefore, it is more suitable for removing the heat by means of liquid medium (e.g., water or antifreeze mixture of water and ethylene glycol).

Other part of the structure of the fifth heat sink is the same as that of the second heat sink, and the detailed description thereof is omitted herein.

The insulating seal 207 is suitable not only for the fifth embodiment, but also for the other embodiments of the present invention.

Sixth Embodiment

FIGS. 6A and 6B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the sixth embodiment of the present invention. The heat sink of the sixth embodiment is a multi-channel flat heat sink with the fin. The difference between the sixth embodiment and the first embodiment is that one or multiple fins 208 are provided on the inner walls of each medium channel 204 along the longitudinal direction of the medium channel 204. The fin 208 may be parallel to the medium channel 204 or spiral-shaped, i.e., the fins 208 are provided on the inner walls of the medium channel 204 in a spiral manner. The fin 208 can increase the medium disturbance, the heat transfer area, cooling capability and efficiency. Of course, it is possible that only a part of the medium channels 204 may be provided with the fin 208. Other part of the medium channels 204 may not be provided with the fins 208 so as to have a smooth inner wall surface.

Other part of the structure of the sixth heat sink is the same as that of the first heat sink, and the detailed description thereof is omitted herein.

The fins 208 is suitable not only for the sixth embodiment, but also for the other embodiments of the present invention.

Seventh Embodiment

FIGS. 7A and 7B are respectively a perspective schematic view and a cross-sectional view of the heat sink applicable to the electromagnetic device according to the seventh embodiment of the present invention. The heat sink of the seventh embodiment is a multi-channel flat heat sink with the fin. The difference between the seventh embodiment and the first embodiment is that the cross-sectional shape of the medium channel 204 is circular-shaped. The inner wall of the medium channel 204 is provided with the fins 208. The structure and arrangement of the fin 208 is the same as that of the sixth heat sink and the detailed description is omitted herein. In addition, the manufacture method of the heat sink of the seventh embodiment may include the following steps: punching multiple holes spaced apart from each other and arranged in a row on a thick metal plate as the medium channel 204, the portion between adjacent medium channels 204 acting as the supporting structure 203; defining the opening 205 communicating with the medium channel 204 and corresponding to each medium channel 204 on one side. The one side may correspond to the second panel 202, and the opposite side may correspond to the first panel 201. The multiple openings 205 may be totally defined on the first panel 201 and not on the second panel 202, or on both the first panel 201 and the second panel 202.

The heat sinks mentioned in several specific embodiments of the present invention are applicable for the electromagnetic device. The heat sink of the present disclosure can be applied to the electromagnetic device such as single-phase iron core reactor, three-phase iron core reactor, hollow reactor, single-phase transformer and three-phase transformer. In addition to electromagnetic device, the present heat sink with the structure mentioned above can be applied to some power components such as power switch and power module.

In light of the technical solution mentioned above, one or more of the advantages and positive effect of the heat sink applicable for electromagnetic device in the present disclosure are as follows.

The first panel, the second panel and the supporting structures in the present heat sink may together constitute a plurality of medium channels for the cooling medium flowing through. The openings are defined on at least some of medium channels, and the close conductive loop is not formed at any cross section of the medium channel with the opening.

The first panel, the middle substrate and the supporting structures together with the second panel, the middle substrate and the supporting structures may constitute two layers of multiple medium channels for cooling medium flowing through. The openings are defined on at least some of medium channels, and the close conductive loop is not formed at any cross section of the medium channel with the opening.

Therefore, with the use of the present heat sink to dissipate heat from electromagnetic device, no conductive loop is formed at the medium channel with the opening in spite of alternating magnetic field generated from electromagnetic device. Thus, the eddy current loss caused by eddy current phenomenon is reduced. The present heat sink is applicable to the electromagnetic equipment.

Meanwhile, the openings are defined on the first panel and/or the second panel, a total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel. Therefore, while ensuring no conductive loop formed at the medium channel, the areas of the first panel and the second panel are maximally persevered, i.e., the heat transfer areas between the heat sink and the electromagnetic device are maximally persevered. Thus, the cooling capability and effect of the present heat sink are improved.

And it should be noted that the above embodiments is only illustrated for describing the technical solution of the invention and not restrictive, and although the invention is described in detail by referring to the aforesaid embodiments, the skilled in the art should understand that the aforesaid embodiments can be modified and portions of the technical features therein may be equally changed, which does not depart from the spirit and scope of the technical solution of the embodiments of the invention. 

What is claimed is:
 1. A heat sink applicable for electromagnetic device comprising a first panel, a second panel, and a plurality of supporting structures connecting with the first panel and the second panel, wherein the first panel, the second panel and the supporting structures together constitute a plurality of medium channels for cooling medium flowing therethrough, wherein at least some of the medium channels are provided with openings formed on the first and/or second panels, and no close conductive loop is formed on cross section perpendicular to a cooling medium flowing direction of the medium channels with the openings, and wherein a total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel.
 2. The heat sink according to claim 1, wherein each medium channel is provided with an opening, the openings on the first panel alternate with those on the second panel.
 3. The heat sink according to claim 1, wherein each medium channel is provided with an opening, all of the openings are defined on the first panel or on the second panel.
 4. The heat sink according to claim 1, wherein the first panel is parallel to the second panel.
 5. The heat sink according to claim 4, wherein the first panel and the second panel are flat-shaped or arc-plate-shaped.
 6. The heat sink according to claim 1, wherein the first panel, the second panel and the supporting structures are made of metal material.
 7. The heat sink according to claim 1 wherein the cross section of the medium channel has a rectangular shape, a triangular shape, a trapezoidal shape, a circular shape or an oval shape.
 8. The heat sink according to claim 1, wherein at least some of the medium channels are provided with at least one fin.
 9. The heat sink according to claim 8, wherein the fin is parallel to the medium channel or has a spiral form.
 10. The heat sink according to claim 1, wherein at least one of the openings is provided with an insulating seal.
 11. A heat sink applicable for electromagnetic device comprising a first panel, a second panel, a middle substrate between the first panel and the second panel, and a plurality of supporting structures connecting with the first panel and the middle substrate and connecting with the second panel and the middle substrate respectively, wherein the first panel and the middle substrate and the supporting structures together with the second panel and the middle substrate and the supporting structures constitute two layers of multiple medium channels for cooling medium flowing therethrough, wherein at least some of the medium channels are provided with openings formed on the first and/or second panels, and no close conductive loop is formed on a cross section perpendicular to cooling medium flowing direction of the medium channels with the openings, and a total area of all openings on the first panel is less than 50% of an area of the first panel, a total area of all openings on the second panel is less than 50% of an area of the second panel.
 12. The heat sink according to claim 11, wherein the opening is defined on each medium channel, the openings defined on the first panel correspond to or alternate with those on the second panel.
 13. The heat sink according to claim 11, wherein the first panel, the second panel and the middle substrate are parallel to each other.
 14. The heat sink according to claim 13, wherein the first panel, the second panel and the middle substrate are flat-shaped or arc-plate-shaped.
 15. The heat sink according to claim 11, wherein the first panel, the second panel, the middle substrate and the supporting structures are made of metal material.
 16. The heat sink according to claim 11, wherein the cross section of the medium channel has a rectangular shape, a triangular shape, a trapezoidal shape, a circular shape or an oval shape.
 17. The heat sink according to claim 11, wherein at least some of the medium channels are provided with at least one fin.
 18. The heat sink according to claim 17, wherein the fin is parallel to the medium channel or has a spiral form.
 19. The heat sink according to claims 11, wherein at least one of the openings is provided with an insulating seal. 